Table 1.
Currently available Förster Resonance Energy Transfer (FRET) biosensors for cAMP, cGMP, and PKA activity.
| Biosensor | Sensitivity | Advantages/Disadvantages | References |
|---|---|---|---|
| CNGC -subunit wildtype C460W/E583M mutant |
cAMP EC50 = 36 μM cGMP EC50 = 1.6 μM cAMP EC50 = 1 μM |
Low cAMP/cGMP selectivity. Restriction to the subsarcolemmal compartment | [53,55] |
| FRET based biosensors: | |||
| FlCRhR (PKA based) | cAMP EC50 = 90 nM | Chemical labeling, purification and microinjection Relatively slow kinetics | [64] |
| R-CFP, C-YFP (PKA based) | cAMP EC50 = 0.5–0.9 μM | Multimeric. Here and below: genetically encoded | [72–74] |
| PKA-camps (PKA based) | cAMP EC50 = 1.9 μM | Single-chain architecture | [78] |
| AKAR1-3 | Not applicable | Measures PKA catalytic activity in real time | [79–81] |
| AKAR4 | Not applicable | Improved dynamic range | [82] |
| Epac1/2-camps (Epac based) | cAMP EC50 = 2.4/0.9 μM | Single-chain. Faster kinetics than for multimeric sensors | [78] |
| Epac2-camp300 CFP-Epac-YFP ( DEP,CD) |
cAMP EC50 = 300 nM cAMP EC50 ~ 50 μM cAMP EC50 ~ 15 μM |
High sensitivity Single-chain. Relatively low sensitivity | [104] [84,111,112] |
| ICUE1/2 (Epac based) | cAMP EC50 ~ 10–50 μM | As above | [83,87] |
| HCN2-camps (CNGC based) | cAMP EC50 = 6 μM | Good for cells with high basal cAMP concentrations | [88] |
| CGY-Del1 | cGMP EC50 = 20 nM | Low cGMP/cAMP selectivity | [92,98] |
| Cygnet-1/2 (PKG based) | cGMP EC50 = 1.5/1.9 μM | Single-chain. Relatively low sensitivity and temporal resolution | [90] |
| cGES-DE2/5 (PDE2/5 based) | cGMP EC50 = 0.9/1.5 μM | Small size. Relatively low sensitivity | [98] |
| redcGES-DE5 (PDE5 based) | cGMP EC50 = 40 nM | High sensitivity | [99] |
| cGi-500/3000/6000 (PKG based) | cGMP EC50 = 500/3000/6000 nM | Small size. Relatively high sensitivity and dynamic range. Fast kinetics | [91] |
| Non-FRET sensors: FlincGs cGMP | EC50 = 150nM (δ-FlincG) | Good dynamic range. Rapid kinetics | [108] |